Quality of Lemongrass Leaves under Khamer-Based Agroforestry: Effect of Pruning Intensity and Nutrient Supply on Essential Oil Content

Abstract

Lemongrass (Cymbopogon citratus) is an economically important aromatic crop widely cultivated for its essential oil, yet its productivity under tree-based agroforestry systems in central India remains poorly documented. Pruning directly influences the light environment experienced by understorey crops, with intensive pruning enhancing the availability of photosynthetically active radiation. However, excessive pruning may adversely affect cumulative biomass production and metabolite accumulation. The present study aimed to evaluate the influence of pruning intensity and nutrient management on the essential oil content of lemongrass grown under Gmelina arborea (Khamer)-based agroforestry, and to identify the optimal combination of these practices for maximizing oil yield in such systems. A two-year field experiment (2021–22 and 2022–23) was conducted at a farmer's field in Village Gram Para, Bargi Dam area, District Jabalpur, Madhya Pradesh, India. Four pruning intensities (P0 – no pruning, P25 – 25%, P50 – 50%, and P75 – 75% canopy removal) were assigned as main-plot treatments, and four nutrient management regimes (T1 – inorganic fertilizer at 60:40:40 N:P:K kg ha⁻¹, T2 – organic manure at 3.5 t ha⁻¹, T3 – vermicompost at 15 t ha⁻¹, and T4 – control) as sub-plot treatments, laid out in a split-plot design with three replications. Data were analysed using analysis of variance (ANOVA) appropriate for a split-plot design. Treatment means were compared using the critical difference (CD) at the 5% level of significance. All analyses were performed in SPSS v16.0. Essential oil content (%) was significantly reduced with increasing pruning intensity across both years and pooled data; the unpruned control (P0) recorded the highest pooled mean oil content (0.66%), significantly superior to the most intensively pruned treatment P75 (0.16%). Among nutrient treatments, vermicompost (T3) produced the highest pooled mean essential oil content (0.52%), significantly surpassing inorganic fertilizer (T1) and the control (T4), while T1 and organic manure (T2) were statistically at par. These findings demonstrate that minimal pruning combined with vermicompost application constitutes the most effective management strategy for maximizing lemongrass essential oil quality under Khamer-based agroforestry conditions in central India. The finding shows that P0 and P25 were significantly superior to P75 across all years and have practical implications for agroforestry management in the AABR region. Farmers practising intensive annual pruning (P75) to reduce shade on understorey crops face a substantial trade-off: while light availability may increase, lemongrass essential oil quality — and hence commercial value — is severely compromised.